The present invention relates to a device for sequentially loading bars in an automatic lathe. Specifically it relates to a bar loader having an improved bar guide system.
In the known art there are automatic lathes which receive sequentially by means of special loaders bars from which to make parts or machined sections. The loader inserts axially the end of a bar at the rear of the lathe chuck. The chuck comprises a clamp or headstock which grasps the bar and moves it axially beneath the machining tools for a length predetermined to be the actual length of the work to be machined. After completion of machining of the work it is cut off and the clamp withdraws by running along the bar to return to the starting position, grasp the bar again and again advance to feed beneath the tools the section to be machined. The sequence of operations is repeated until the bar is exhausted. At this point the loader withdraws the remaining bar stub, discards it and inserts a new bar in the lathe so that the machining cycle can resume automatically.
There being inserted in the lathe only a short section of bar head, for the entire machining cycle the bar is supported at the rear by guide means integral with the loader structure. In known loaders, between the feed clamp and bar guide means there is however inevitably created progressively an ever greater space as the clamp moves to push the bar into the lathe. This allows bending and vibration of the bar which disturb machining performed by the lathe. In addition, the resonance vibrations produced in particular at the higher rotation speeds of the bar are difficult to damp by conventional methods of elastic suspension, the resonance frequency continuing to change depending on the breadth of the free space between the clamp and the guides.